The problem of vehicle occupant safety has now become a nation-wide problem for the USA and other countries. More than 95% of American cars are equipped by safety systems such as Supplemental Restraint System (SRS) comprising an air bag. For example, a front air bag restraint system has an air bag, which is deployable between an instrument panel and an occupant seat within an automotive vehicle. When the vehicle includes an occupant restraint device arranged to protect the occupant during a crash involving the vehicle, it can be coupled to the weight measuring system and arranged to provide a variable deployment depending on the determined weight of the occupying item. During a crash event, the vehicle's crash sensor and other sensors provide crucial information to the air bag Electronic Controller Unit (ECU), including collision type, angle and severity of impact etc. Using this information, the air bag electronic controller unit's crash algorithm determines if the crash event meets the criteria for air bag deployment and triggers various firing circuits to deploy one or more air bag modules within the vehicle. Working as a supplemental restraint system to the vehicle's seat belt system, air bag module deployments are triggered through a pyrotechnic process that is designed to be used once. The signals from the various sensors are fed into the air bag computing and control unit, which determines from them the position of the vehicle occupant, the severity or force of the crash, along with other variables. Advanced air bag technologies are being developed to tailor air bag deployment to the severity of the crash, the weight and position of the vehicle occupant, belt usage, and how close that person is to the actual air bag. Many of these systems use multi-stage inflators that deploy less forcefully in stages in moderate crashes than in very severe crashes. Occupant sensing devices let the air bag control unit know if someone is occupying a seat adjacent to an air bag, the mass/weight of the person, whether a seat belt or child restraint is being used, whether the person is forward in the seat and close to the air bag, and other possible parameters.
Under some rare conditions, air bags can injure and, in some very rare instances, kill vehicle occupants. To provide crash protection for occupants not wearing seat belts, recent “smart” air bag controllers can recognize if a seatbelt is used, and alter the air bag cushion deployment parameters accordingly.
To improve safety of passengers in case of a possible crash, adaptive and advanced duel-depth air bag systems were designed according to the Passenger Classification System. Adaptive air bag systems may utilize multi-stage air bags to adjust the pressure within the air bag. The greater the pressure within the air bag, the more force the air bag will exert on the occupants as they come in contact with it. These adjustments allow the system to deploy the air bag with a moderate force for most collisions, reserving the maximum force air bag only for the severest of collisions. Additional sensors to determine the location, weight or relative size of the occupants may also be used. Information regarding the occupants and the severity of the crash are used by the air bag control unit, to determine whether air bags should be suppressed or deployed, and if so, at various output levels.
In the advanced duel-depth air bag, the first and second chambers of the air bag are selectively pressurized with a gaseous fluid. The valve member is operable to distribute the pressurized fluid to one chamber, both of the chambers of the air bag, or to the atmosphere. The design of the advanced duel-depth air bag system shows that the car manufacturers try to improve the vehicle occupant safety employing the Passenger Classification System (U.S. Pat. No. 8,417,422) by multiplying the number of stages of an air bag.
According to one published Passenger Classification System and crash severity information, the air bag in the advanced duel-depth air bag system is deployed at either at a high force level, a less forceful level, or not at all, as following:
45 pounds or less was relayed as an infant or toddler. In this category, the air bag was automatically shut off and would not deploy.
46-108 pounds was relayed as a child or small adult. In this category, depending on the severity of the crash, the low side of the air bag may have been deployed.
109 pounds and above was considered a full size adult. In this category, depending on all other factors, the high side of the air bag may have been deployed.
As we may see from this Passenger Classification System, the force applied by an air bag in the advanced duel-depth air bag system is the same as applied to the person whose weight is 109 Lb and applied to the person whose weight is even 400 Lb or higher. A light occupant in such situation may be injured and heavy occupant may be not protected enough. This is the reason that it is necessary to provide more classes in the Passenger Classification System to differentiate the forces applied to adult occupants in case of collision according to their weight.
In some vehicles, an inflator could produce excessive internal pressure upon deployment. If an affected air bag deploys, the increased internal pressure may cause the inflator to rupture. In the event of an inflator rupture, metal fragments could pass through the air bag cushion material possibly causing serious injury or fatality to vehicle occupants. Past ruptures like this have killed or injured vehicle drivers. There have been reports of severe, and sometimes, lethal injuries due to defective gas generators projecting shrapnel towards the vehicle occupant's face and neck upon air bag deployment. This resulted in a massive recall being issued in the U.S. in 2015 and 2016, involving over 30 million vehicles.
From 1990 to 2000, the United States National Highway Traffic Safety Administration identified 175 fatalities caused by air bags. Most of these (104) have been children, while the rest were adults.
262 deaths from1990 to 2006 reportedly have been caused by air bags inflating in low severity crashes, most of them in older model vehicles. These deaths include 87 drivers, 13 adult passengers, 138 children, and 24 infants.
These statistics show that the number of the victims is indirectly proportional to their weight. It means that to significantly improve safety of the vehicle occupants it is necessary to put stress on controlling the forces applied to the occupants' bodies by more accurately measuring their weights. There are many kinds of sensors and devices designed to measure weight of a vehicle occupant. These sensors are used for measuring the weight of an occupant in a vehicle seat which evaluates the occupancy of the seat and helps to define the location and orientation of the occupant, which is very important in safety systems. These sensors provide a seat pressure or weight measurement system and thereby improve the accuracy of another apparatus or system which utilizes measured seat pressure or weight as input.
In the U.S. Pat. No. 6,076,853 is disclosed an occupant weight measuring system related to bladder sensors and that works in an air bag safety system. The entire contents of U.S. Pat. No. 6,076,853 are incorporated herein by reference thereto. In the U.S. Pat. No. 7,330,784 disclosed a weight measuring system arranged in connection with the support structure of a seat for determining an approximate weight of an occupying item of the seat. The entire contents of U.S. Pat. No. 7,330,784 are incorporated herein by reference thereto. The weight measuring system consists of strain gage sensors, arranged at the rearward and forward locations of the seat. Each sensor provides data relating to the force or pressure being applied at the respective location which is used to derive the approximate weight of the occupant. It is noted that the weight measured here will not be the entire weight of the occupant since some of the occupant's weight will be supported by his or her feet which are resting on the floor or pedals. Contribution of the weight of the foot part of the body to a total weight of a person may be evaluated very easily, and it is about 20-30% of the whole body weight. This is a problem that does not allow to accurately weigh a vehicle occupant in on-board vehicle supplemental restraint system to provide a possibility of an accurate control of the air bag inflation force depending on a real value of the occupant's weight (mass) and eliminate extra force applied to the occupant's body at the time of collision. So, to accurately weigh a vehicle occupant, it is necessary to weigh the whole body of a vehicle occupant including real weight of a foot part of his/her body. It is not made in the SRS system yet.
The Transportation Equity Act for the 21st Century specified that the modern air bag systems should provide improved protection for occupants of different sizes as well as minimize the risk of injury or death from air bags for infants, young children, and other occupants. On May 12, 2000, National Highway Traffic Safety Administration (NHTSA) issued a rule specifying the requirements for such a system.
NHTSA, Department of Transportation, published in August 2004 requirements of the final rule of Section § 571.208 Standard No. 208; “Occupant crash protection” to improve the security of the air bags for children and light passengers.